George Collings fits the ZT50 CRUISE CONTROL from Conrad Anderson

Note: Now renamed the GC50.

One of the main attractions of driving is that it demands total concentration. For nine years I served as a Motor Patrol Constable and found immense job satisfaction in attending emergency calls as safely and quickly as possible. The police system of driving requires the driver to be in complete control of his vehicle at all times, so until lately I have not favoured equipment that reduces the level of driver involvement.

Recently, the Editor asked me if I would like to try a DIY-fit cruise control. The plod (done a lot of that) in the van from Devon up and down the M5 had long lost any novelty value, and my right ankle was in danger of fossilisation, so I said I would give it a go on my VW T4 2.4-litre diesel.

Fitting

The instructions had clear, easily followed, diagrams but are in the process of being rewritten for improved guidance. The first job was to decide where to locate various components. The magnets that provide information for the speed sensor must go on the drive shaft, and the clutch switch on the pedal lever, but the others have to be found suitable spaces.

Before starting work I took the usual safety precaution of disconnecting the battery.

The command module is quite small. I hate drilling unsightly holes in expensive areas of trim, and in this, case it was unnecessary as the basic T4 dash has an easily knocked out black plastic blank -in a position that will allow fingertip operation with hands on the steering wheel. To bring the module to the correct angle I carved a wooden wedge-shaped plinth, painted it matt black and screwed it to the blank. The module is fixed to the plinth with double-sided tape and its wiring passes into the dash though a small I slot cut in the blank.

To give a smooth run to the accelerator cable the actuator is best sited in the engine compartment. VW's five-cylinder unit is a snug fit and the only practical place was on the bulkhead just above the air cleaner. The vacuum supply is easily taken off the line from the engine-driven vacuum pump to the brake servo (via a VW-provided tapping).

On first inspection, access to the accelerator lever on the injection pump looks about nine on a ten-point difficulty scale. But the T4 has a party trick up its sleeve. If three self-tapping screws are removed and the front grille taken off, then four bolts unscrewed to remove the top cross-member, the whole radiator can be lifted and pulled forward five inches on swivel mountings. It only takes two minutes and leaves plenty of space at the front of the engine. (The designer who came up with this (Big Hans?) definitely had dirt under his fingernails earlier in his career.) Connecting the actuator and accelerator cables is easy -using the kit's cable throttle clamp to fix the outers and allen-keyed (key supplied) cable clamp for the inner cables.

Next to be fitted is the control module. This is best housed indoors in the warm. There was no obvious place until I unscrewed the plastic caps holding the rubber mats in place just to the right of the accelerator pedal. Behind the mat was a thick sound insulation pad that had a small moulded basin shape projecting out to support the rubber mat. With a sharp knife I pared away a top quarter of the dome so that just over half of the module sat with its bottom fixing tag slotting into the dome. A self- tapping screw then secured the top tag of the module to the insulation pad. This gave the module a well protected home with enough room to run the wiring and multipin connector to it.

Next in line was the speed sensor. The 'van went up on ramps so I could drop the undertray to get easy access. Only two out of the three slotted magnets provided are needed and they are evenly spaced around the inner constant velocity joint. Double-sided tape is used to initially position the magnets before they are strapped-on by cable ties passed though the slots. I had problems getting the tape to stick but I suspect that was due to working in a temperature of minus two degrees centigrade all together aaah!). The sensor bracket, to be mounted on a differential housing bolt, was made from one of the lengths of predrilled steel strip in the kit. It had to be cut, bent to a right angle, one of the holes drilled-out to suit the bolt, and then trimmed to allow a snug fit around webs on the differential casing. It could have been done with just a hacksaw and vice, but I also used a bench grinder.

The clutch and brake switches came next. One of the more awkward areas of a vehicle to work on is around the top of the pedals. Eyes need relocating onto the ends of your fingers, and ideally lighting would come from fibre optics under the fingernails. Having none of this equipment -I fell back on the occasional glimpse, and touch, to fit the magnetically-operated reed switch to the clutch pedal and unclip the brake light switch to tap into its wiring.

Another length of predrilled strip bolted to ! the pedal box made the bracket for the reed switch. I tucked the double-sided tape in my pocket to warm, before successfully using it to stick the magnet to the clutch pedal and the reed switch to its bracket.

With all the components in place, just three Scotchlok connections had to be made to wire up the clutch and brake switches. The fused feed was taken from an ignition key controlled slot on the main fuse board, and the earth connection bolted to the chassis. As the system can be transferred to other vehicles, rather than cut excess lengths of wiring I tidied it into coils (held with insulation tape) and made sure everything was safely tied or clipped out of harm's way before plugging all the connections together. It was time to reconnect the battery. Just in case there is a short I always very gently touch the battery clamp to the battery post. With a bit of luck, if there is a big fat spark the connection can be broken before much harm is done. It takes much longer to disconnect the battery if the initial connection is rammed home hard.

The ZT50 has built-in diagnostic modes that allow one to check basic functions whilst static. On the road the system was a little sluggish at first, but there is a three-position sensitivity setting on the electronic module and the highest setting cured the problem.

The system works in a very unobtrusive manner. Increases in power to match a hill are very smooth, and the transition to overrun on a descent is virtually undetectable.

One dark evening shortly after installing the system, I had chance to try it out on the particularly boring run west on the M5 across the Somerset Levels. We had been away for the weekend and a cold I had picked up meant I was feeling decidedly under the weather. Basically, all I wanted to do was potter along with the heavies in the nearside lane. After accelerating up to 58 mph I engaged the control. There was a truck running about 300 yards ahead and very soon it was obvious that he was also using cruise control, as I was keeping station behind so steady that there had been no change when he turned off 25 miles on. Boredom could have been a problem, but without the distraction of an aching ankle I felt better able to pay attention to the steady stream of overtaking traffic. All in all, I arrived home after the one-and-a half-hour run much fresher than expected.

One of the problems with the hilly West Country roads is that my 2.4-litre diesel T4 coach built motorcaravan frequently does not have enough power to maintain a set cruising speed uphill. Then, as is intended, the ZT50 either disengages on changing gear, or when speed drops below 75 per cent of that set. This mode of operation probably suits petrol engines well, but is not quite right for many diesels that can pull down to much lower speeds). It only means you have to press the reset button once speed is regained, and would be much less apparent on vehicles with a better power-to-weight ratio.

Conclusion

This is a decent quality kit that can be fitted by a competent DIY person. A Freephone technical helpline is available in case of difficulty.) I took three days to fit the kit, as I did some other work at the same time and it was freezing weather. In ideal conditions it will take about a day.

The system operates as intended. The more powerful your vehicle the more use it will be, and the more help it could be to keep a clean license. At a cost of £149.95 the kit looks good value for money. (A model with stalk-mounted control costs £175.95.) On a payback basis there should be an improvement in fuel consumption for some drivers more than others) but it would only need to prevent a couple of speeding tickets don't forget to add in the increased insurance for an endorsement) to pay for itself. A reduction in driver fatigue can only be good accident prevention.

The kit is available from Conrad Anderson, 57 Sladefield Road, Ward End, Birmingham B8 3PF. Tel: 0121-247 0619. Fax: 0121-247 0974.
Web site: www.conrad-anderson.co.uk